120mm or 115mm rod on 10DM? Piston info?

[trickedcarbine]

 I got a deal on some Mattoon DM cases. So, better luck with 120mm or 115mm rods? How is piston availablility if I go 120mm?

[sleeper06]

I wonder if anyone has done any R+D on pro/con through the rpm range 

[registered user]

as a general rule your better off with the longer one. it goes back to the friction loss thing between long and short. but for availabilty reasons you may be forced to use the short one, if the long one is rare and hard to find. with the longer one there may  also be a small benefit from the lower primary compression ratio depending if u have a rather high ratio now. longer one may also be structurally stronger since longer rods are typically used in larger capacity engines. some of this is speculation as i dont know anything about your engine or 120 rods. i like the idea of the longer one, if for nothing else but the friction standpoint but i know some hard to find rods can be 200-$300 each 

[JTmachining]

Use a builder

[registered user]

could a 125mm rod from a common motox engine be used? those r cheap and easy to find

[JUSTWANNARACE]

10dm will be fine with a 115 rod but limited to mostly CP for pistons. 120 rod there are shelf pistons you can use but require machine work. Plus the dwell time on the longer rod will make it slower to rev. Anything above 64mm stroke I would move to the 120.  But I know nothing

[JUSTWANNARACE]

And might as well do a 14-16mm would be basically the same cost

[registered user]

110 rod would b fine for a while also. imo theres a big difference between being fine and being perfectly reliable for many years.  people forget that often times your using larger heavier piston, doubling the power and increasing rpm 2000-3000 more rpm. maybe claude could put the numbers in his nifty FEA program and show how the shorter stockish rods compare to longer beefier stuff

 

even if u could show the shorter ones revs a bit faster, i think its kind of a weak argument in the big picture but thats just me

[JTmachining]

 I got a deal on some Mattoon DM cases. So, better luck with 120mm or 115mm rods? How is piston availablility if I go 120mm?

I got 18mm parts u need